Telephone ringer cam

ABSTRACT

A CAM FOR VARYING THE LOUDNESS OF TELEPHONE RINGERS BY LIMITING CLAPPER TRAVEL, SAID CAM BEING MADE OF RESILIENT MATERIAL WITH A SERIES OF SPACED APART RIDGES EXTENDING FROM EITHER SIDE TO ABUT UPON ADJACENT MOUNTING SURFACES AND COMPENSATE FOR THE VARIATIONS IN TORQUE WHICH RESULT FROM CUMULATIVE TOLERANCE VARIATIONS AND DIFFEREING CAM POSITION.

Nov. 9A, 1971 T. PECAK l 3,618,421

TELEPHONE RINGER CAM Filed March 13, 1970 FIG. 1

2O 1a \s 2928 FIG. 2

1e Non \S INVIJN'IURy TADEU SZ PECAK Agent United States Patent O 3,618,421 TELEPHONE RINGER CAM Tadeusz Pecak, London, Ontario, Canada, assigner to Northern Electric Company Limited, Montreal, Quebec,

Canada Filed Mar. 13, 1970, Ser. No. 19,316 Int. Cl. F16h 53/00 U.S. Cl. 74-567 6 Claims ABSTRACT OF THE DISCLOSURE This invention relates to members which are subject to variable loads between opposed surfaces and more particularly to cams for use in controlling the sound output of telephone ringers.

It is a common feature of telephone design to provide means for controlling the volume of the ringer or bell. Generally, the ringer comprises an oscillating clapper ball mounted within a gong cavity and the control is a radial cam movable about a shaft by means of a lever, into a variable number of positions in the clapper ball travel path to vary the ringing volume through control of the clapper travel. The composition of the cam has previously been neoprene or an equivalent material and of uniform cross-section so that when mounted on the aforementioned shaft it was securely held between a control lever and an upper ring.

This prior structure has had several shortcomings. It is essential -that the stress to which the cam is subjected be limited to a range which at the lower-end ensures that minimal shocks do not vary the adjustment, and at the upper end is not so great that the cam is permanently set so that the torque is minimal, or such that the adjustment is ltoo diicult to make.

These requirements have been ditlicult to achieve in prior structures principally because the cam is subjected to pure compression with very little room for material displacement.

It is therefore a principal object of this present invention to provide an improved cam for use in controlling the sound output of telephone ringers.

It is another object of the present invention to provide an improved cam structure for telephone rin-gers which will accommodate a wider range of manufacturing tolerances to minimise the pressure variations to which the cam member may be subject and which will be economical to produce In accordance with the present invention there is provided a bendable -rnember adapted to be subjected to variable loads between opposed surfaces comprising: a substantially planar annular portion having a hole therein to permit passage of a shaft therethrough; a plurality of spaced apart ridges extending out from said planar portion in a load equalizing relationship to abut upon said opposed surfaces.

Other objects and features of the invention will be more apparent from the following description and drawings in which a preferred embodiment is described by way of example and in which:

FIG. 1 is a fragmentary plan view of a telephone ringer cam assembly employing a cam member in accordance with the present invention;

3,618,421 Patented Nov. 9, 1971 FIG. 2 is a section taken yalong line 2 2 of FIG. 1 illustrating the cam 15 in a free, uncompressed state, prior to staking.

FIG. 3 is a further section taken along line 2-2 of FIG. l under working or staked pressure conditions and serves to illustrate the mechanism for minimizing differentials.

Referring now to the drawing, there is illustrated in FIG. 1 a fragmentary plan view of a telephone ringer employing in 4the cam assembly a cam member in accordance with the present invention. As shown, a clapper assembly, generally indicated at 11, is mounted within a gong, the wall of which is indicated at 10. The ringing noise of the telephone is produced by oscillation of a clapper ball 12; the loudness of the ring is dependent upon the distance that ball 12 is permitted to travel. The travel in turn governed by the position of a cam edge '14 of a cam 15.

The support and mounting for cam 15 is provided by a post or stake '16 disposed centrally of the gong with a central upwardly extending rod of reduced diameter 17 which together with post 16 provide a seat for noise adjustment arm 18. The noise adjustment arm is provided with a hole 19 adjacent its inner end so that it will sit upon the shaft 17 and its outer end extends beyond the gong to permit adjustment by movement around rod 16. Upon the upper surface 20 of arm 18 cam member 15 is seated and held in engagement therewith by means of discs or washers 21 and '22 and a suitable fastening means such as a staking flange, screw or rivet 23.

With the prior art, it has been found that variations in the height of the shaft 17 and in the thickness of the disc or plate 21, the arm 18 and the cam 15 will lead to a variation of pressure upon the said cam member 15 so that under excess pressure there will be a great deal of torque or under insuicient pressure there will be insu'icient torque, leading either to difficulty of adjustment or even a permanent set as described previously.

ICam member 15 comprises a rst substantially annular portion 25 which has a central hole 26 with a ridge 27 extending upwardly, and ridges 28 and 29 extending downwardly. It is to be noted that the disposition of ridges 27, 28 and 29 is staggered with respect to each other. External to ridge 27 on the upper surface of portion '15 there is provided a step 30 with a rounded edge. And again outward of step 30, the laterally extending radial cam portion 15 projects in the manner shown in FIGS. l and 2. From the upper surface of cam 15, a stud'31 extends and` this stud, together with a pair of chordally disposed studs 32 on the remote side of annular portion 25 ensure a facility for locating the disc 21 on the cam member 15 thus ensuring correct location of same on the shaft or rod 17. The provision of these studs avoids substandard mounting and possible damage to the tools or the top edge of the rod 17. They centre the disc 21. The provision of step 30 ensures that cam 15 is not distorted after staking in operation.

The cam member 15 and its annular portion 25 are integrally moulded of polyurethane or any equivalent elastic or resilient material which will not assume a permanent set under conditions referred to herein. In View of the elastic properties of the cam, it is necessary to provide a downwardly extending rib such as 33 about the edge of cam 15 to give the structure peripheral rigidity without promoting excessive tapping noise due to clapper 12.

In order to adjust the ringing noise of the telephone, the subscriber will normally move arm 18 in accordance with the dotted arrow shown in FIG. 1. With a movement of the arrow in either direction, there will be a correspondit will vary the travel of the clapper 12. The movement 3 of the arm 18, by virtue of engagement with the under surfaces of ridges 28 and 29 of cam 15, will be transmitted thereto, and in View of the fact that the ridge 27 engages with the under surface of the disc or plate 21, there will also be a transmittal of a stress through these points of engagement.

The cam assembly when compressed and staked, or fixed by other means, assumes a configuration shown in FIG. 3, the stress to which the cam member 15 is subjected will not vary substantially within the limits of manufacturing tolerances of the component parts. As shown in FIG. 3, the ridges such as 27, 28 and 29 are on a staked assembly compressed and deformed and move laterally to fill the channels which they define with neighbouring ridges and with the adjacent components of the assembly. As shown in FIG. 3, the sides of ridges 27, 28 and 29 have been urged outwardly due to the pressures now exerted upon them but the pressure variation is minimized or compensated for by the bending of the annular portion 25 rather than the purely compressive characteristics which existed in the prior art in which no means were provided for compensating for the variation in pressure. It will also be noted that ridges 28 and 29 are substantially equally disposed on either side of ridge 27 or staggered so that the load is equally distributed.

While the present invention has been described with respect to a preferred embodiment in a specific application, it will be obvious to those skilled in the art that the principles employed may be equally applicable in other situations where members may be subjected to variations in pressure between two plates.

What I claim as my invention is:

l. A cam member of resilient material adapted to be subjected to variable loads between opposed surfaces cornprising:

an annular portion having a hole therein to permit passage of a shaft therethrough;

a plurality of spaced apart ridges extending out from said annular portion to abut upon said opposed surfaces in a load equalizing relationship; and

a planar portion extending laterally from Said annular portion, the planar portion providing a cam surface extending normal to said planar portion.

2. A cam as claimed in claim 1 wherein said ridges extend from said annular portion on each side thereof in a spaced apart staggered relationship.

3. A cam member as claimed in claim 1 wherein at least one annular ridge extends from one side of said portion to about against a rst of said surfaces, and at least two annular ridges extend from the other side of said annular portion to abut upon a second of said opposed surfaces, said ridges on said respective sides being spaced apart from said hole and each other with said oppositely extending ridges being staggered.

4. A cam member as claimed in claim 1 wherein said planar portion includes a peripheral reinforcing ridge extending downwardly at least around said cam surface.

5. A bendable member as claimed in claim 2 wherein said cam member is of a resilient synthetic polymer material.

6. A cam member as claimed in claim 3 wherein said annular portion and said planar portion each include at least one outwardly extending locating stud.

References Cited UNITED STATES PATENTS 2,878,464 3/1959 Ham, Jr., et al. 340-402 X 3,212,353 10/1965 Caapin et al, 74--567 3,481,219 12/1969 De Rosa 74-568 WILLIAM F. ODEA Primary Examiner F. D. SHOEMAKER, Assistant Examiner U.S. Cl. X.R. 74-568; 340-402 

